I have been having a look at various documents today and I think we can 'short-circuit' the fault finding exercise in favour of going straight to the potential culprit.
The most likely culprit is IC401 (LM379) Dual 6W Audio Amplifier used to drive the scan coils.
First (with the power OFF) check for continuity (with your multimeter) from the NEGATIVE side of capacitor C411 (1000 uF) to pins 3, 4, 11 and 12 of IC401.
We are expecting very low resistances. Any open circuits could mean PCB track damage.
Note: In the measurements below, the Voltage shouldn't exceed +/- 9V (under normal circumstances) but it is always wise to start off with a high V/div setting and work your way down.
With the power ON (and suitable safety precautions to avoid contacting any high voltages around the CRT), use your oscilloscope to measure the voltage waveform on pins 8 [Y direction] and 7 [X direction]. The voltage should be oscillating both above zero and below zero. Note the indication on the oscilloscope of Vmax and Vmin. You will need to choose a suitable timebase to see some vectors being drawn (i.e. the voltages varying that you are measuring).
If both of the pins you are measuring (7 and 8 of IC401) indicate both positive and negative voltages (with respect to 0V/GND of course) then everything up to the amplifier IC401 should be fine.
Next, measure the output pins of IC401 at 10 [Y direction] and 5 [X direction].
Again, you should observe the voltage going both positive and negative (relative to 0V/GND). I would like to bet that one pin (pin 5 - X direction) will either always be positive OR negative.
If this is the case, IC401 (LM379) is most likely faulty.
Dave